This invention relates to torque limiting clutches adapted for general application with power transmission machinery and particularly to torque limiting clutches having axial pressure engagement of the friction surface by helical springs such that no adjustment is required at installation or as the friction surface wears down.
It is common practice in the machinery drive art to provide spring loaded, friction-type torque limiting clutches in the drive train to prevent damage from extremely high shock loads or machinery jams. In operation, machinery such as mining machinery, transmits a shock load through the drive to a clutch that slips and thus limits the shock load within the drive machinery. Though prior art torque limiting clutches have gained commercial acceptance, they exhibit certain drawbacks. The proper torque setting is dependent upon the skill of the assembler in adJusting the spring load on the friction surface. Also, after a period of functioning to relieve overload shock, the friction surfaces would wear and thus a readjustment of the load springs would be required to compensate for the wear and maintain the necessary pressure on the friction surfaces to properly operate the drive. If wear proceeds without adjustment, clutch torque is apt to diminish to the point that common friction-type torque limiters will slip and the friction surfaces will burn, damaging the clutch and losing the ability to function. Further, when the prior art torque limiting clutches are readjusted for wear, they are often over-adjusted too tightly and thus the shock load protection capability is lost which results in severe damage to the drive machinery.
Previously known torque limiting clutches have generally been bulky, unnecessarily adding size, weight, and complexity to the associated machinery. Further, such clutches have provided means for locking input drive shafts only at an end of the input hub, failing to accommodate the insertion of short shafts from either end of the hub. These known clutches have also failed to provide a wear indicator to advise the operator when normal acceptable wear of the friction surfaces has been exceeded. Finally, with all of the shortcomings above, the prior art clutches have remained of complex design, not given to ease of assembly or repair.
This invention is directed to a novel torque limiting clutch that overcomes the problems previously experienced.